I’m thinking upgrade my low pressure HWC to main pressure. I can see the vent pipe stick out from my roof. Would be a hole there when I upgrade to Main pressure? Would be way to seal it off or cap it as the vent pipe no longer required.
Plumber should resolve it. I imagine they would just leave it in place and take some measures to stop the odd rain drop from ending up in your home, such as connecting it to the drain line, or capping it off.
Theoretically the plumber could also use the vent pipe as the discharge for the pressure relief valve the mains pressure system, assuming they accounted for the additional head of water when selecting the valve set point. No idea if this is permitted in the plumbing rules.
our plumber just cut the pipe by the roof and then capped it.